Research On Cohesive Zone Model And Its Application In Failure Analysis Of Automotive Thin-Walled Composite Structures Under Impact

Thin-walled composite structures are widely used in automotive bodies,such as windshield laminated glass with millimeter thickness and automotive coating with micron thickness.Investigation of the failure mechanism of automotive thin-walled composites under impact is of great significance for structural optimization and vehicle safety.In view of the finite element method,this paper carried out a series of investigations based on the famous fracture model,cohesive zone model(CZM).First,an extrinsic solid-shell CZM is proposed.Although the solid element-based CZM can effectively simulate material failure,it faces a great challenge of computational efficiency in fracture of thin-walled composites,where internal force requires high computational cost.In view of this,an extrinsic solid-shell CZM is proposed.Compared with the solid element,the adopted pentahedral solid shell element is more suitable for the modeling of thin-walled structures,and the internal force calculation efficiency is higher.For fracture problems with simple cracks,cohesive elements are adaptively inserted into the solid-shell elements during the calculation to reduce the number of elements.An efficient cell-based algorithm,LC-Grid,is used for global searching in complex contact calculations.The proposed model is verified by several numerical examples.Then the model is applied to a drop-weight test of a laminated glass plate.The simulated glass crack and the acceleration response of the impactor are both in good agreement with the experimental results,which further verifies the effectiveness of the model.The computational efficiency of the proposed model in terms of internal force is three times that of the solid element-based CZM.Second,an intrinsic solid-shell CZM is proposed.For efficient simulation of the windshield with large-scale complex fracture patterns,an intrinsic solid-shell CZM,which is suitable for parallelization,is proposed.In this model,the cohesive element is inserted into the solid-shell element before calculation,and the bilinear traction-separation law is used to describe failure during the cohesive region.The effectiveness and efficiency of the model are verified by two groups of numerical examples.The model is then applied to the fracture of windshield laminated glass under impact of dummy headform.The dynamic crack process of glass and the acceleration response of dummy headform are all successfully captured,which verifies the ability of the developed model in problems with complex fracture patterns.Finally,a GPU-based parallel computing framework of CZM is established.In order to greatly improve the computing efficiency of the CZM,this paper resorts to the CPU/GPU hybrid programming concept of CUDA FORTRAN to realize the parallel computing of the intrinsic solid-shell CZM.Besides,a complete GPU parallel computing framework including internal force,CZM,contact,rigid body,and kinematic update is established.Meanwhile,a finite element solver,FTW-GPU,which is suitable for impact failure simulation of thin-walled composites is developed.Simulation of the test of an aluminum-based organic coating system subjected to single-particle impact is carried out.Aimed at the large-scale 3-D finite element model of coating,an efficient coating finite element model is proposed where solid elements and solid-shell elements are separately used to model the contact region and other regions of the coating sample.The GPU parallel CZM is used to describe the debonding behavior between coating and substrate.The simulated coating debonding area is in good agreement with experimental outcomes in literature.When the number of elements is about 200 thousand,the total speedup of computational efficiency is 136.5,and the speedup in terms of kinematic update reaches 332.5.The GPU parallel method of CZM can be used as a powerful tool for the impact failure simulation of automotive thin-walled composite structures.